Shortly after bloc v5 and flutter_bloc v5 were released—with the major change of introducing cubit as the foundation for state management and building bloc on top of it—Felix Angelov quickly followed up with bloc and flutter_bloc v6. The key change in this version brings cubit inside bloc itself, rather than having it as a dependency that bloc calls upon. Along with other improvements and bug fixes, let’s dive into what’s new.
cubit
As mentioned, in this version bloc has fully integrated cubit as part of its core. To recap, cubit is one of the state management approaches that follows a similar philosophy to BLoC—separating logic from UI to keep the UI as simple as possible. The intermediary (usually called BLoC) evaluates incoming Events and determines what State to transition to, handling any external data requirements along the way.
Using cubit is simpler, as it eliminates Events entirely and instead uses function calls for updates. This should feel familiar to developers coming from other languages with similar state management patterns. In this version, Felix has brought cubit into bloc and discontinued the standalone cubit package. Of course, the original bloc remains available, now built on top of cubit but using Event-based management.
Breaking Changes
The main breaking change affects how Observers subscribe to Blocs. In previous versions, subscribing would immediately yield the current state as the first state. In v6, this no longer happens—subscribers must wait for the next state instead. This adjustment better aligns with Dart Stream behavior.
Other changes include onError in BlocObserver now accepting Cubit as its first parameter, and the addition of initial state emission capabilities for both bloc and cubit.
For flutter_bloc, all widgets that previously accepted a bloc parameter have been renamed to use cubit instead for greater accuracy. This applies to the following widgets: BlocBuilder, BlocListener, BlocConsumer
Other Changes
Additional changes include adding onChange to BlocObserver, introducing various Linter rules, and adding the @visibleForTesting annotation to emit in Cubit for testing purposes. General documentation improvements were also made.
📚 Hope you enjoy reading!